taap.digitalnetwork engineering toolkit

How many /64 subnets are in a /48?

Answer
65,536 /64 subnets in a /48

The difference between the prefix lengths is 64 − 48 = 16 bits, so a /48 holds 216 = 65,536 /64 subnets. A /48 is the standard enterprise site allocation; every LAN segment gets a /64.

subnet6 · adjust the values

The math

2(64 − 48) = 216 = 65,536

The subnet ID lives in the fourth hextet. Each /64 is one LAN with 264 interface addresses, enough for SLAAC.

First subnets of 2001:db8::/48

#/64 subnet
12001:db8::/64
22001:db8:0:1::/64
32001:db8:0:2::/64
42001:db8:0:3::/64
65,5362001:db8:0:ffff::/64

Addresses are written in RFC 5952 form: lowercase, no leading zeros, longest zero run compressed to ::.

Planning tip

Keep subnet boundaries on nibbles (multiples of 4 bits) so each subnet ID maps to whole hex digits and reverse DNS (ip6.arpa) delegation stays clean. Encode structure (site, function, VLAN) in those digits rather than allocating sequentially.

More questions like this

/64 in a /56/64 in a /60/64 in a /52/48 in a /32/48 in a /40/48 in a /44/56 in a /48/64 in a /32

Frequently asked questions

How many addresses are in each /64?

264 addresses. That is one LAN segment; never size it by host count.

How many /64s are in a /48?

65,536 (216).